1. Field of the Invention
The present invention relates to an antiglare film, an antireflection film, a polarizing plate and an image display device.
2. Description of Related Art
In various image display devices such as liquid crystal display device (LCD), plasma display panel (PDP), electroluminescent display (ELD) and cathode ray tube display device (CRT), an antiglare film or an antiglare antireflection film is used on the display surface so as to prevent reduction in the contrast due to reflection of outside light or disturbing reflection of an image. With widespread usage of the image display device in an office or household environment, it is required to enhance the antiglare property of preventing a fluorescent lamp in room or the viewer's figure from causing disturbing reflection on the display surface and more improve the display contrast in a bright place.
The antiglare film that is inexpensive and capable of mass production includes an antiglare film obtained by coating a resin containing a light-transmitting fine particle on a surface of a transparent substrate film to form an antiglare layer. However, the light-transmitting fine particle contains a coarse particle attributable to the particle production, and the coarse particle disadvantageously becomes a point defect at the production of an antiglare film and decreases the production yield of the antiglare film. Accordingly, for removing the coarse particle with good precision, a method of previously performing a filtration treatment of the light-transmitting fine particle in an emulsion state or liquid dispersion state has been developed (see, for example, JP-A-2005-309399).
However, the previous filtration treatment of the light-transmitting fine particle makes it difficult to produce an antiglare film that is inexpensive and capable of mass production, because the light-transmitting particle is very expensive and the productivity of the light-transmitting fine particle decreases.
Also, for preventing disturbing reflection of outside light, an antireflection film having an antireflection layer on the antiglare layer of the antiglare film is generally used. The antireflection film has an action of reducing the reflectance by using the principle of optical interference so as to prevent the reduction of contrast due to reflection of outside light or disturbing reflection of an image and is disposed on the outermost surface of a display. Furthermore, the disturbing reflection of outside light can also be suppressed by the effect of surface scattering by providing appropriate irregularities on the surface of the antireflection film.
However, when an antireflection layer is tried to be coated on the irregular surface of the antiglare layer, coating unevenness attributable to irregularities or repelling attributable to the coarse particle is generated, failing in obtaining a uniform thickness, and optimal light interference as designed is not brought about, as a result, the reflectance may not be decreased. For this reason, it has been difficult to satisfy both low reflection and antiglare property.